Automotive fuel pumps using rotary pumping elements, in general, and regenerative turbines in particular, have been used for many years. Such pumps typically have two-piece pump housings within which the impeller or turbine is rotated by an electric motor. Examples of such pumps are shown in U.S. Pat. No. 4,403,910 and U.S. Pat. No. 4,445,821, both to Watanabe et al., and U.S. Pat. No. 4,451,213 to Takei et al. The pump housings illustrated in these patents are typical of prior art devices inasmuch as the housings are generally comprised of two main parts, with the impeller operating in a chamber defined by the two pieces of the pump housing.
Those skilled in the art will appreciate that the performance of rotary pumps in general, and regenerative turbine pumps in particular is greatly dependent upon the ability to operate the pump with minimum internal leakage. Specifically, if the pumped fluid, in this case motor fuel, is permitted to flow radially across the sides of the impeller, the performance of the pump will be greatly degraded. To avoid such degradation, the clearances between the impeller and the pump housing must be exceedingly small. This requirement may cause problems during manufacturing with the illustrated and conventional prior art pump housings because it is not an easy task to repeatably build fine toleranced parts required in the pump housing and then match such parts to the impeller. This problem stems from the fact that the tolerances applied to individual parts may stack up to produce an unacceptable result in the assembled pump. If, on one hand, the clearances between the impeller and the pump housing are too great, the performance of the pump will be inadequate. If, on the other hand, the tolerances are too little, the pump may not work at all, or the motor may fail at an early age due to excessive drag imposed by the pump assembly.
It is an object of the present invention to provide an automotive fuel pump with a modular pump housing which offers superior pump performance.
It is another object of the present invention to provide an automotive fuel pump which may be manufactured with ease using conventional manufacturing techniques.
It is yet another object of the present invention to provide a method for manufacturing high performance automotive fuel pumps in an economical manner.
It is yet another object of the present invention to provide a pump having a structure which is manufacturable using more robust processes than those employable with prior art units. Specifically, prior art pump housings are generally not compatible with the surface finishing process known as "lapping" because lapping is best used in connection with flat surfaces, and not with dished or multi-planar surfaces. A pump according to the present invention uses three major modules which may all be finished by lapping on large, flat lapping machines, at lower cost.
Other objects, features, and advantages of the present invention will become apparent to the reader of this specification.